Question

Show how you would determine the number of neutrons in a Chlorine atom that has a mass number of 37 ?

Another atom of Chlorine has a mass number of 35. How does it compare to the atom of Chlorine in the above question ?

Answer 1

we know chlorine atom atomic number is 17 . that means it has 17 protons .

number of protons = Z = 17

the mass number is already given that is 37

mass number = A = 37

formula for number neutrons = A - Z

= 37 - 17

= 20

number of neutrons = 20 -----------------------> answer (1)

anothe chlorine atom mass number is 35. but atomic number is same that is 17. in this chlorine number of neutrons are different 35- 17 = 18 .

so Cl-37 and Cl-35 both have same atomic number and different mass number or different number of neutrons.

so these are called isotopes

definition for isotopes : elements with same atomic number but different mass number are called isotopes